It is known that a treatment of cellulose materials under the coexistence of 2,2,6,6-tetramethyl-1-piperidine-N-oxyradical (hereinafter referred to as TEMPO) and an inexpensive oxidizing agent, sodium hypochlorite, allows an efficient introduction of carboxyl groups to the surface of cellulose microfibrils. The thus obtained, oxidized cellulose may be converted to a homogenous, transparent aqueous dispersion liquid of cellulose nanofibers by an addition of a small defibration energy. Such methods for manufacturing oxidized cellulose and methods for manufacturing cellulose nanofibers have been studied widely (PTL 1).